Hassall's corpuscles (also known as thymic bodies) are structures found in the medulla of the human

thymus The thymus (: thymuses or thymi) is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus ...

, formed from

eosinophilic Eosinophilic (Greek suffix '' -phil'', meaning ''eosin-loving'') describes the staining of tissues, cells, or organelles after they have been washed with eosin, a dye commonly used in histological staining. Eosin is an acidic dye for stainin ...

type VI thymic epithelial cells arranged concentrically. These concentric corpuscles are composed of a central mass, consisting of one or more granular cells, and of a capsule formed of epithelioid cells. They vary in size with diameters from 20 to more than 100μm, and tend to grow larger with age. They can be spherical or ovoid and their epithelial cells contain keratohyalin and bundles of

cytoplasm The cytoplasm describes all the material within a eukaryotic or prokaryotic cell, enclosed by the cell membrane, including the organelles and excluding the nucleus in eukaryotic cells. The material inside the nucleus of a eukaryotic cell a ...

ic fibres. Later studies indicate that Hassall's corpuscles differentiate from medullary thymic epithelial cells after they lose

autoimmune regulator The autoimmune regulator (AIRE) is a protein that in humans is encoded by the ''AIRE'' gene. It is a 13Kilo-base pair, kbp gene on chromosome 21q22.3 that encodes 545 amino acids. AIRE is a transcription factor expressed in the Thymus#Medulla, me ...

(AIRE) expression. This makes them an example of Thymic mimetic cells. They are named for Arthur Hill Hassall, who discovered them in 1846. The function of Hassall's corpuscles is currently unclear, and the absence of this structure in the thymus of most

murine The Old World rats and mice, part of the subfamily Murinae in the family Muridae, comprise at least 519 species. Members of this subfamily are called murines. In terms of species richness, this subfamily is larger than all mammal families excep ...

species (except for the New Zealand White Mouse strain) has previously restricted mechanistic dissection. It is known that Hassall's corpuscles are a potent source of the

cytokine Cytokines () are a broad and loose category of small proteins (~5–25 kDa) important in cell signaling. Cytokines are produced by a broad range of cells, including immune cells like macrophages, B cell, B lymphocytes, T cell, T lymphocytes ...

TSLP. ''In vitro'', TSLP directs the maturation of

dendritic cells A dendritic cell (DC) is an antigen-presenting cell (also known as an ''accessory cell'') of the mammalian immune system. A DC's main function is to process antigen material and present it on the cell surface to the T cells of the immune system ...

, and increases the ability of dendritic cells to convert naive thymocytes to a Foxp3+ regulatory T cell lineage."Old mystery solved, revealing origin of regulatory T cells that 'police' and protect the body"
/ref> It is unknown if this is the physiological function of Hassall's corpuscles ''in vivo''. In the past decade, researchers found tissue-specific self-antigens in Hassall's corpuscles and revealed their role in the pathogenesis of diseases such as type 1 diabetes,

rheumatoid arthritis Rheumatoid arthritis (RA) is a long-term autoimmune disorder that primarily affects synovial joint, joints. It typically results in warm, swollen, and painful joints. Pain and stiffness often worsen following rest. Most commonly, the wrist and h ...

multiple sclerosis Multiple sclerosis (MS) is an autoimmune disease resulting in damage to myelinthe insulating covers of nerve cellsin the brain and spinal cord. As a demyelinating disease, MS disrupts the nervous system's ability to Action potential, transmit ...

, autoimmune thyroiditis, Goodpasture's syndrome, and others. They also discovered that Hassall's corpuscles synthesize chemokines affecting different cell populations in thymic medulla. Despite this, the information on the relationship between Hassall's corpuscles with other cell types of thymic medulla (dendritic, myoid, neuroendocrine cells, thymocytes, macrophages, eosinophils, etc.) remains insufficient and often contradictory. Mechanisms of these relationships and their functional significance are still unclear. The lack of such data does not allow a systemic view of the differentiation processes in the thymus.

References

External links

* * * "Hassall's Corpuscles" * - "Thymus" * - "Lymphoid Tissues and Organs: thymus, Hassall's corpuscles" {{Portal bar, Anatomy Histology